A normal heart sound signal was shown in Figure 3(a). There were two major components within a normal beat, the first heart sound(S1) and the second one (S2). In comparison to Figure 3(a), there were additional components,S3 and S4, during diastolic periods (S2-S1 interval) in Figure 4(a). The amplitudes of S3 and S4 were smaller than S1 and S2 with great varieties.